The torch-on method of roofing involves unrolling sheets or strips of granular tarpaper onto a roof deck and using a torch to adhere the sheets to the deck. This method continues to develop adherents in the roofing trade. It has a number of advantages over the more conventional tar and gravel method. Torch-on roofing is easy to apply in high or awkward places because it does not require that heavy materials or equipment be lifted to the job site; a roofer can generally complete a job with nothing but rolls of torch-on roofing paper and a few hand-tools such as a trowel and a torch. Applying torch-on roofing is also less environmentally damaging than applying tar and gravel roofing because a torch and special roofing paper replace the unpleasant large vat of molten tar.
The torch-on roofing paper ("torch-on") is generally a special tarred or rubberized paper with a granulated upper surface and a smooth heat sensitive lower surface. The granules on the upper surface are present to help protect the torch-on sheet against deterioration caused by the sun's ultraviolet rays. The lower surface is smoothly coated with a tar-like substance that, when heated, tends to adhere to roof decking or another sheet of torch-on.
Applying sheets of torch-on is a straightforward procedure. Essentially, a sheet is laid smooth-side down onto the roof deck and a torch is swept over top of the sheet to heat the smooth underside and make it adhere to the deck. However, lap joints between sheets, and stripping around obstructions such as HVAC units, pose particular problems to forming a weatherproof seal. In these locations, the granulated upper surface of the lower sheet prevents it from fully abutting the smooth, lower surface of the upper sheet, as is necessary for a good bond.
"Degranulation" is the key to producing good lap joints and stripping. Degranulation refers to the preparatory step of smoothing the granulated upper surface of a sheet of torch-on so that it can form a better bond with the smooth lower surface of an adjacent sheet. If the degranulation step is skipped, the resulting bond will be weak and may not form a weatherproof seal.
The conventional method of degranulating a sheet of torch-on is both tedious and time consuming. A roofer snaps a chalk line on the granulated upper surface of the lower sheet along the line of the desired seam. Following the chalk line as a guide, the roofer, on hands and knees, heats the granulated surface with a torch and then smoothes the molten granules with a trowel. The roofer must produce a smooth, even bonding surface that closely follows the chalk line. Unfortunately, this critical step demands a high degree of roofing skill. In a trade known for high labor turnover, a critical but tedious step like degranulation either will be done poorly by an inexperienced junior roofer or will demand undue attention from a senior roofer who could be more productively employed at other parts of the job.
Large sealing and seaming machines are known in the general roofing trade. For instance, U.S. Pat. Nos. 4,259,142 granted to Kortepeter, 4,504,352 granted to Meyer, and 4,725,328 granted to Arnold teach the use of various movable machines that fuse sheets of roofing material using heat and pressure. However, these machines are more akin to miniature steamrollers than to the type of hand-tools used in the torch-on sector of the roofing trade. Significantly, these machines do not independently degranulate the lower sheet of roofing material in preparation for fusing, but instead apply heat to both sheets and then press them together.
What is needed is a better tool for degranulating torch-on. There is a need for an inexpensive, portable degranulator that will permit a low skilled worker to degranulate torch-on sheets quickly and accurately.